实体框架-更新表中的一行

Question

I am new to Entity Framework and i have a question regarding updating data in a table.

Currently, I am using the following approach to update data and looking for a better way if somebody can help me out.

Let's say I am updating "Category" table and it has only 3 fields(id, name, archived)

private void UpdateCategory(category entity)
{
    category  catObj = context.category.find(e=> e.id == id);
    catObj.name = entity.name;
    catObj.archived = entity.archived;
    context.savechanges();
}

My question is if there are 50 fields in category table I will have to assign each field individually. Can't i do something like this .. catObj = entity; ?

Answer 1

To do this automatically you could probably use a project such as AutoMapper .

However you have to be careful with this, because if a property doesn't have a value for the category being passed in, it will overwrite the old category's property with the non-value, even if it's not intended. To get around this you will have to use automapper configurations to do the projection correctly, exactly as you want.

Answer 2

You can change the properties of all members of a collection with a single LINQ operation:

collection.Select(c => {c.PropertyToSet = value; return c;}).ToList();

So:

private void UpdateCategory(category entity)
{
    category  catObj = context.category.find(e=> e.id == id);
    catObj.Select(c=> {c.name = entity.name; c.archived = entity.archived; return c;}).ToList();
    context.savechanges();
}

Answer 3

I am not sure that AutoMapper is good for your purpose. Also you may have to specify mappings anyway.

For what you described, I usually have a method such as void CopyEntityFrom(Category Source) in each entity and in the method, I have mapping statements (eg this.name = entity.name; ) But I do this not by hand but generate them using MVCScaffolding or other code generation techniques.